Homogeneous armor plate



Nov. 3, 1936 F. RITTERSHAUSEN HOMOGENEOUS ARMOR PLATE Filed Oct. 27,1932 off/5 9.. 0 6 6. 1w. 2. 0. 8 6. 1+. l a. 6.. rv. r9. 5 ,5 5 5 1t b.L. h. 1+

v Ritented Nov. '3, 1936 UNITED sTATEs PATENT OFFICE'l 2,059,746HOMOGENEOUS ARMOR.y PLATE Fritz Rittershausen, Essen, Germany, assignerto Fried. Krupp Aktiengesellschaft, Essen-onthe-Ruhr, Germany applicati@october 27, 1932, serial No. 639,881

. In Germany December 15, 1931 Claims.

5 and showing a uniform texture on its entire cross section, that is aplate which for example is not hardened on one side or cemented andhardcned.

The known homogenous armor plates of high- 1o est quality are made fromsteel alloys which con.-

tain about 0.25 to 0.35% carbon, 3 to 5% nickel, l

1 to 1.8% chromium and sometimes up to 0.5%

` molybdenum, the addition of molybdenum serving in these known armorplates to facilitate the heat treatment and to avoid the danger oftempering brittleness. The nickel is considered as the bearer of thetoughness, and since great value is attached to very high toughness, thenickel content generally is fixed at 3.5% at least.

Exhaustive researches have now shown that the toughness of armor platesand thus' their resistance to striking projectiles, especially toyoblique fire, and their safety against being pierced by bursting shells,is not only not reduced but can even be considerably improved byreducing the nickel content to about 3% or less, provided the carboncontent is -kept on about 0.12 to 0.42% and the chromium content on 2 toabout 3.75%, and molybdenum is present in the alloy in an amount from-0.2 to 1%, while the total of chromium and nickel should lnot be higherthan indicated by the curve A of the acg companying drawing. It is ofparticular advantage so to determine the composition of the armor platesthat it comes .within the hatched area B of the drawing, wherein thecompositions situated in the upper part thereof and containing highertotals of chromium and nickel are especially suited for thickerp1ateswhilst for plates of smaller thickness the compositions comingwithin the lower part of the area B are especially flt. The effect ofthe molybdenum may be obtained also by about 1.5 to 3 times as muchtungsten. In certain cases the nickel may be entirely dispensed with.The cause of the superiority explained above of the proposed compositionof armor plates is to be seen, in the opinion of the inventor, inthefeature that in heating the plates the Aci critical point, which mustnot be exceeded in the heat treatment following the hardening treatment,is substantially higher in the new armor plates than with the knownplates richer in nickel, so that it is possible to reheat the new plateseven at tempera- 56 tures up to about '100 C. This higher reheating (Cn.14s-21.5)

treatment, however, which cannot be employed with the known plates,richer in nickel and poorer in chromium, imparts to the plates asubstantially higher toughness and thus a substantially improvedresistance to being damaged by pro- 5 jectiles. For heat treated armorplates, that is plates of the above composition and hardened andreheated in the above-described manner show a, notch toughness of about35 mkg/cm (normal Charpy test) and a tensile strength of 10 aboutlig/mm2. y

The same high toughness, butwith e. slightly lower tensile strength, canbe obtained, by virtue of the high critical point, even by a simpleheating at temperatures up to about 750 C. 15

The armor plates forming the subject-matter of the present invention aredistinguished for the advantage of having a substantially higherresistance to projectiles and of being manufactured at substantiallylower costs,.owing to the m nickel content being smaller or dispensedwith altogether.

Particularly advantageous examples of the armor plates according to theinvention are the following:

1. Homogeneous armor plate of 'l0 mm. thickness, containing about 0.2%carbon, 2.4% chromium, 0.4% `molybdenum, no nickel.

2.' Hom'ogeneous armor plate of 100 mm. thickness, containing about0.19% carbon, 2.3% 30 chromium, 0.4% molybdenum and 1.5% nickel.

3. Homogeneous armor plate of mm. thickness, containing about 0.32%carbon, 2.6% chromium, 0.6% nickel, and-0.38% molybdenum.

4. Homogeneous armor plate of mm. thlck- 35'- ness, containing aboutA0.39% carbon, 2.5% chromium, 1.8% nickel and 0.45% molybdenum,

What I claim and desire to secure by Letters Patent is:-

1. The process of heat treating a homogeneous v40 armor plate made froma steel alloy containing about 0.12 to 0.42% carbon, about 2 to 3.75%chromium, an appreciable amount of nickel not Over about 3%, and metalselected from the group molybdenum, tungsten in the proportion 0.2 to 451% molybdenum, 0.3 to 3% tungsten, the remainder substantially all iron,the total-of chromium and nickel referred tothe carbon content being nothigher than indicated by the curve A of the drawing, which processconsists in harden- 50 ing the plates throughout by a uniform heattreatment and reheating them at a temperature of about '700 C.

2. The process oi heat treating a homogeneous armor plate made from asteel alloy containingy about 0.12 to 0.42% carbon, about 2 to 3.75%chromium, an appreciable amount oi' nickel not over about 3%, and metalselected from the group molybdenum, tungsten in the proportion 0.2 to 1%molybdenum, 0.3 to 3% tungsten, the remainder substantially all iron,the carbon and chromium plus nickelcontent of which comes within thearea B of the drawing, which consists in hardening the plates throughoutby a unii'orm heat treatment and reheating them at a temperature ofabout 700 C. g

3. Homogeneous armor plate made from a steel alloy containing about 0.12to 0.42% carbon, about 2 to 3.75% chromium, an appreciable amount ofnickel not over about 3%, and metal selected from the group molybdenum,tungsten in the proportion 0.2 to 1% molybdenum, 0.3 to 3% tungsten,

the remainder substantially all ironr the totalof chromium and nickel,referred to the carbon content, being not higher than indicated by thecurve A of the drawing, said steel alloy being in a substantiallyhomogeneous hard and tough condition throughout resulting from ahardening heat treatment followed by reheating to about 700 C.

4. Homogeneous armor plate made from a steel v-alloy containing about0.12 to 0.42% carbon,

about 2 to 3.75% chromium, an appreciable amount of nickel not overabout 3%, and about 0.2 to 1% molybdenum, the total of. chromium andnickel, referred to the carbon content, being not higher than indicatedby the curve A of the drawing,fsaid steel alloy being in a substantiallyhomogeneous hard and tough condition throughout resulting from ahardening heat treatment followed by reheating to about 700 C., saidplate being characterized by a particularly high resistance topenetration by projectiles.

5. Homogeneous armor plate made from a steel alloy containing about 0.12to 0.42% carbon, about 2 to 3.75% chromium, an appreciable amount ofnickel not over about 3%, and metal selected from the group molybdenum,tungsten in the proportion 0.2 to 1% molybdenum, 0.3 to 3% tungsten, theremainder substantially all iron, the nickel content being at a gurebetween the limits stated determined according to a direct ratio betweenthickness of the armor plate Aand nickel content, the total ofy chromiumand nickel, referred to the carbon content, being not higher thanindicated by the curve A of the drawing, said steel alloy being in a.substantially homogeneous hard and tough condition throughout resultingfrom a hardening heat treatment followed by reheating to about 700 C. y

FRITZ RI'ITERSHAUSEN.

